In many environments, it is desirable for some individuals to be made aware of incoming telephone calls, but at the same time undesirable for others to be disturbed by the loud ringing that typically results with some present-day installations. In environments such as restaurants, bookstores, department stores, libraries, etc., it is often the case that it is necessary for loud ringing to permeate the atmosphere. In some cases, ringing signals resulting from incoming telephone calls are broadcast over a public address system so as to insure that they will be heard, which can be annoying and unpleasant for customers, particularly when the calls are not answered, which often happens.
This problem is on the surface solvable by making use of some form of paging receiver that is carried by individuals, such as the paging receivers now commonly used by individuals outside of a building. Several drawbacks result from such an approach, however. Radio is relatively expensive because of the cost of paging receivers, and also requires substantial energy, limiting battery life. In addition, radio bandwidth is required, involving possible licensing or the need to deal with paging companies (and paying monthly service fees), and also raising the possibility of signal delays that could substantially delay the receipt of a paging signal after a ring was received.
An alternative is the use of some other medium that is particularly useful within a building. Thus, for example, the Curtin invention (U.S. Pat. No. 3,657,715) discloses a paging system for use in a building using ultrasound, in which an ultrasonic signal at a frequency unique to a given individual is transmitted over a power line to a set of transducers that converts the signal to sound and is received at an ultrasonic detector carried by an individual. Similar systems, including those by Lester (U.S. Pat. Nos. 3,696,384, 3,805,227, and 3,805,265) disclose variations that use ultrasound and other media, sometimes in combination, including infrared light, radio, baseband wire, or other media, to allow paging of individuals. Such systems typically also allow tracking individuals, with the Ward invention (U.S. Pat. No. 3,439,320) using ultrasound for tracking the location of individuals and routing incoming telephone calls to the room that a given individual is in when the call arrives.
The primary problem with such systems is the potential for failure. Potential customers of such systems are reluctant to buy them if there is any possibility of failure. Failure is not just a matter of factors that impair transmission, such as electromagnetic interference or shielding that might impair radio waves, visual obstructions that might impair infrared light, or auditory obstructions that might impair ultrasound. Failure of a system also results when a user forgets to carry the unit on a particular day, or leaves it on one's desk when at lunch and then forgets to carry it after lunch, or goes out to the parking lot and takes the unit with him or her. Failure can also result from a drained battery or defective electronics. It is a primary object of the present invention to provide a system that is "fail safe" and will always result in effective alerting of users to an incoming telephone call regardless of any of these forms of failure.
An invention by Brown, et al. (U.S. Pat. No. 5,222,123) has some similarity in mechanism to the present invention. Brown, et al. discloses a cordless telephone system that redirects calls. A user who desires to be reached at another location will program that location to expect the user at a certain time. When a caller places a call to the user, the central office will redirect the call to a base station, which sends a polling signal by radio to the cordless telephone. In the embodiment most similar to the present invention, of the cordless telephone is near the base station, it will respond and a call will be set up. However, if the cordless telephone does not respond, the base station will so indicate and the central station will redirect the call to a different location, such as the location the original call was placed to. The present invention is directed to receiving calls at a single fixed location and insuring that at least one individual will be alerted to such an incoming call.
Another invention by Emery, et al. (U.S. Pat. No. 5,469,496) also has some similarity to the present invention. Emery, et al. discloses a system for integrating wired and wireless telephone systems, in particular cordless telephones that have a base station unit that is connected to the wired telephone system. Emery, et al. is particularly concerned with providing flexibility in routing calls and in routing calls in a manner customized to the particular needs of individuals. In the version of the Emery, et al. invention most similar to the present invention, a base station sends a signal to a cordless handset, with the handset responding by indicating that the handset is busy (e.g., already on a call), is ringing, or is unavailable (out of range). In the case of the handset ringing, the base station waits for a certain specified number of rings and then, if the handset has not answered, the call is redirected to a different line or service, such as transferring the call to a secretary's line or to a voicemail system or answering machine. In contract, the goal of the present invention is to insure that the alerting signal resulting from an incoming call is effectively and quickly (and quietly, if possible) transmitted so as to notify an individual or individuals that the incoming call has arrived, even if they forgotten to wear their alerting device or it has malfunctioned. In the present invention, the incoming call is accepted on the same line and at the same telephone station regardless of whether the individual is alerted by a signal from a wearable alerting unit or by a broad range auditory ringer. The call itself is not rerouted if the alerting unit does not respond.